Performance evaluation of cryogenically treated tungsten carbide tools in turning

This paper describes a study on the effects of cryogenic treatment of tungsten carbide. Cryogenic treatment has been acknowledged by some as a means of extending the tool life of many cutting tool materials, but little is known about the mechanism behind it. Thus far, detailed studies pertaining to cryogenic treatment have been conducted only on tool steels. However, tungsten carbide cutting tools are now in common use. The main aim of this study is to analyze the differences in tool performance between cryogenically treated and untreated tool inserts during orthogonal turning of steel. This will aid in the quest for optimal cutting conditions for the turning of steel using these inserts, and will also enhance the understanding of the mechanism behind the cryogenic treatment of tungsten carbide, and the changes in its properties after cryogenic treatment. In the process of ascertaining these findings, it was shown in this study that under certain conditions, cryogenic treatment can be detrimental to tool life and performance. It was also shown that cryogenically treated tools perform better while performing intermittent cutting operations.     

Investigation of the effects of cryogenic treatment applied at different holding times to cemented carbide inserts on tool wear

Cutting tool costs is one of the most important components of machining costs. For this reason, tool life should be improved using some methods such as cutting fluid, optimal cutting parameters, hard coatings and heat treatment. Recently, another one of the methods commonly used to improve tool life is cryogenic treatment. This study was designed to evaluate the effects of different holding times of deep cryogenic treatment on tool wear in turning of AISI 316 austenitic stainless steel. The cemented carbide inserts were cryogenically treated at −145 °C for 12, 24, 36, 48 and 60 h. Wear tests were conducted at four cutting speeds (100, 120, 140 and 160 m/min), a feed rate of 0.3 mm/rev and a 2.4 mm depth of cut under dry cutting conditions. The wear test results showed that flank wear and crater wear were present in all combinations of the cutting parameters. However, notch wear appeared only at lower cutting speeds (100 and 120 m/min). In general, the best wear resistance was obtained with cutting inserts cryogenically treated for 24 h. This case was attributed to the increased hardness and improved micro-structure of cemented carbide inserts. These improvements were confirmed through hardness, image processing, and XRD analyses.     

Influence of welding parameters on microstructure and wear behaviour of a typical NiCrBSi hardfacing alloy reinforced with tungsten carbide

Wear parts which are exposed to severe abrasive conditions must withstand high wear demands. Abrasive loading superposed with impact due to abrasive particles are a dominating wear mechanism restricting lifetime in many different industries, for example mining and farming. In practical application, different welding technologies such as plasma transfer arc (PTA), metal active gas (MAG) and laser are used to form wear resistant materials. The aim of this study is to evaluate the influence of welding parameters on the microstructure and wear behaviour of these wear resistant materials using MAG welding technology. To simulate real field conditions on a lab-scale, tests were performed with a standard ASTM G65 dry-sand rubber-wheel tester (3-body abrasion). In order to investigate impact abrasion, a special impeller-tumbler apparatus was designed and used for wear tests (combined impact and abrasion wear). Wear tests were performed on Ni-based alloys containing large amounts of hard phase.Within this work it was shown that welding parameters such as current intensity and number of layers strongly influence dilution with the base material and furthermore the formation of transition zones between welding layers and overlap zones. Concerning wear behaviour it was found that high content of uniformly distributed tungsten carbides in a metallic matrix show the best behaviour under a condition of pure abrasion, whereas under cyclic impact loading (high energy level) massive breaking of the tungsten carbides results in a high wear regime, compared to martensitic materials which perform best.     

深冷处理对YG10硬质合金磨损性能的影响

以YG10硬质合金为研究对象,深冷处理技术为手段,采用正交试验的方法,在不同深冷温度、深冷时间、交变次数的情况下对其进行深冷处理,并对处理后的试样进行磨损试验、硬度试验和显微组织分析试验.结果表明,最优深冷处理工艺使YG10合金显微硬度提升33.6％,耐磨性提升72.8％,深冷温度是影响YG10合金耐磨性能最大的因素....     

深冷及深冷后回火处理对截齿硬质合金头耐磨性的影响

选取YG8硬质合金作为掘进机截齿硬质合金头的材料,研究深冷工艺和深冷后回火工艺对YG8硬质合金耐磨性和平均摩擦因数的影响,并通过扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)探究两种工艺对YG8硬质合金相组织的影响.结果表明,深冷后回火处理在减少YG8硬质合金磨损量方面更明显.深冷处理在降低YG8硬质合金...     

磁场深冷处理对YG11C硬质合金耐磨性的影响

基于深冷处理提供的温度场和永磁体提供的匀强磁场,对YG11C硬质合金进行磁场深冷处理,并与常规工艺和深冷处理工艺进行了对比分析.结果表明:深冷处理较常规处理,其耐磨性提高了约35％,磁场深冷处理相应降低了约21％.在微观机理上,深冷处理后合金中η相碳化物数量增加是耐磨性提高的主因.磁场深冷新工艺处理后,合金中α-Co向...     

Tool wear and machining performance of cBN–TiN coated carbide inserts and PCBN compact inserts in turning AISI 4340 hardened steel

PCBN is the dominant tool material for hard turning applications due to its high hardness, high wear resistance, and high thermal stability. However, the inflexibility of fabricating PCBN inserts with complex tool geometries and the prohibitive cost of PCBN inserts are some of the concerns in furthering the implementation of CBN based materials for hard turning. In this paper, we present the results of a thorough investigation of cBN plus TiN (cBN–TiN) composite-coated, commercial grade, carbide inserts (CNMA 432, WC–Co (6% Co)) for hard turning applications in an effort to address these concerns. The effect of cutting speed and feed rate on tool wear (tool life), surface roughness, and cutting forces of the cBN–TiN coated carbide inserts was experimented and analyzed using analysis of variance (ANOVA) technique, and the cutting conditions for their maximum tool life were evaluated. The tool wear, surface roughness, and cutting forces of the cBN–TiN coated and commercially available PCBN tipped inserts were compared under similar cutting conditions. Both flank wear and crater wear were observed. The flank wear is mainly due to abrasive actions of the martensite present in the hardened AISI 4340 alloy. The crater wear of the cBN–TiN coated inserts is less than that of the PCBN inserts because of the lubricity of TiN capping layer on the cBN–TiN coating. The coated CNMA 432 inserts produce a good surface finish (<1.6 μm) and yield a tool life of about 18 min per cutting edge. In addition, cost analysis based on total machining cost per part was performed for the comparison of the economic viability between the cBN–TiN coated and PCBN inserts.     

An experimental study of tool wear and cutting force variation in the end milling of Inconel 718 with coated carbide inserts

Inconel 718 is a difficult-to-cut nickel-based superalloy commonly used in aerospace industry. This paper presents an experimental study of the tool wear propagation and cutting force variations in the end milling of Inconel 718 with coated carbide inserts. The experimental results showed that significant flank wear was the predominant failure mode affecting the tool life. The tool flank wear propagation in the up milling operations was more rapid than that in the down milling operations. The cutting force variation along with the tool wear propagation was also analysed. While the thermal effects could be a significant cause for the peak force variation within a single cutting pass, the tool wear propagation was believed to be responsible for the gradual increase of the mean peak force in successive cutting passes.     

A study on the effect of tool nose radius in ultrasonic elliptical vibration cutting of tungsten carbide

Nowadays, ultrasonic elliptical vibration cutting (UEVC) technique is being successfully applied for ultraprecision machining of difficult-to-cut materials. Previous study reported that the tool geometry especially tool nose radius notably influences the performance of 1D ultrasonic vibration cutting (UVC). However, the effect of tool nose radius in the UEVC technique is yet to be studied. This study aims to investigate the effects of tool nose radius on the UEVC performance in terms of cutting force, tool wear and surface finish when machining a hard-to-cut material, sintered tungsten carbide (WC), using PCD tools. The experimental results show that the UEVC technique performs remarkably better in all aspects at a 0.6 mm nose radius compared to a lower (e.g. 0.2 or 0.4 mm) and a higher nose radius (e.g. 0.8 mm). When machining about 412 mm² surface area, an average surface roughness, R_a of 0.010 μm is achieved with a 0.6 mm nose radius. Analyses are conducted to justify the findings in this study.     

Effects of cryogenic treatment and refrigerated air on tool wear when machining medium density fiberboard

Cooling of cutting tools with liquid coolants and lubricants is impractical when machining dry wood or wood composites. This study examines the combined effect of cryogenic tool treatment and using refrigerated air for cooling tools on reducing tool wear. A total of four, double-flute, solid, tungsten carbide router bits were used to machine medium density fiberboard with a CNC router. Three of the four tools were cryogenically treated to below −149 °C. During cutting, refrigerated air was applied to two tools, while the other two cut at ambient temperature. All tools were examined under the stereo light microscope to capture images in order to measure tool wear. Elemental analysis was performed using scanning electron microscopy to determine the percentage of specific elements present on clearance faces of tools after cutting was completed. Results show that less tool wear occurs when using refrigerated air and cryogenic treatment, thereby increasing tool life when cutting medium density fiberboard.     

PCBN刀具干车淬硬钢时倒棱前角对切削力和刀具磨损的影响

PCBN刀具磨出负倒棱是为了加强刀具的刃口强度，以减少刀具加工时可能出现的破损情况。本文通过对PCBN刀具加工淬硬轴承钢GCr15的一系列试验数据加以分析，得出倒棱前角和切削力、刀具磨损之间的关系，进而得出在实际加工情况下应该采用的最佳倒棱前角值。试验表明：当倒棱前角取15度且切削速度为125m／s时，刀具具有最好的加工效果，不但切削力可以达到最小值，刀具磨损最轻，而且刀具寿命也达到了最大值。     

PcBN刀具车削镍基高温合金切削性能研究

本文研究了刀尖圆弧半径、负倒棱参数、切削速度、PcBN材质及干湿切削对PcBN刀具车削镍基高温合金GH4169切削性能的影响.试验结果表明:增大刀尖圆弧半径、负倒棱角度或减小负倒棱宽度均会使刀具磨损相应减小;PcBN的磨损随切削速度的提高而增大;DBW85的切削性能优于BZN6 000和BTN100,且其高速下的磨损量...     

Effect of the lubrication-cooling technique, insert technology and machine bed material on the workpart surface finish and tool wear in finish turning of AISI 420B

The paper is focussed on the effects produced by cutting operations on workpiece surface finish and tool wear. To this end, finish turning of AISI 420B stainless-steel was carried out under wet, minimum quantity of lubricant and dry cutting conditions, using both conventional and wiper technology inserts, on turning centres equipped with beds made in polymer concrete and cast iron. The workpiece surface finish and tool wear versus cutting volume were measured, and the results analysed and discussed in detail. The most significant results were: (i) the lubrication-cooling technique does not significantly affect the tool wear, whilst wet cutting produces the worst surface finish, (ii) the wiper inserts allow obtaining of the best surface finish, and (iii) the use of polymer concrete bed leads to an improved behaviour in terms of tool wear and surface roughness.     

热处理工艺轿车同步器齿环用HMn59-2-1-0.5合金磨损性能的影响

制定了国产HMn59-2-1-0.5合金同步器齿环的热处理工艺, 对比了该合金齿环和进口齿环的磨损性能, 分析了HMn59-2-1-0.5合金的磨损机理.结果表明: 国产HMn59-2-1-0.5合金同步器齿环耐磨性优于进口同步器齿环或与之相当, 磨损机理主要是磨粒磨损, 热处理后形成的"硬质点 软基体"和"软质点 硬基体"的典型多相复合耐磨组织使合金具有良好的摩擦特性.